Hibernoma Showing High Uniform Accumulation on an 18F-Fluorodeoxyglucose Positron Emission Tomography Scan: A Case Report

BACKGROUND Hibernoma is a rare, benign, soft tissue tumor arising from brown fat that cannot be distinguished from other lipogenic tumors on computed tomography and magnetic resonance imaging (MRI) scans. On the other hand, the image of hibernoma on 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) is different from that of other lipogenic tumors. However, fewer studies have investigated the typical features of hibernoma on PET scans. We present the case of a hibernoma that was incidentally detected on 18F-FDG-PET. CASE PRESENTATION A 48-year-old Asian man underwent 18F-FDG-PET for routine follow-up of gastric cancer. The patient reported a painless soft mass on the upper arm that had persisted for several years. On 18F-FDG-PET, the mass showed a maximum standardized uptake value of 9.6. The mass showed high intensity on T1- and T2-weighted MRI scans, and showed focally enhanced septa after gadolinium administration. The mass was surgically resected. Histopathologically, the mass was composed of brown adipose cells characteristic of hibernoma. His postoperative course was uneventful, and there was no local recurrence at the final 24-month follow-up. CONCLUSION Hibernoma showed strong uniform accumulation on 18F-FDG-PET, suggesting that 18F-FDG-PET would be a useful modality for the differential diagnosis of hibernoma versus other lipogenic tumors.